# Problem with ComboBox, output errors

**URL:** <https://forum.kirupa.com/t/problem-with-combobox-output-errors/239184>\
**Category:** flash\
**Created:** [September 19, 2007, 12:38pm UTC](https://forum.kirupa.com/t/problem-with-combobox-output-errors/239184 "2007-09-19T12:38:56Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![dfm\_](https://avatars.discourse-cdn.com/v4/letter/d/3da27b/32.png) [@dfm\_](https://forum.kirupa.com/u/dfm_)\
**Post date:** [September 19, 2007, 12:38pm UTC](https://forum.kirupa.com/t/problem-with-combobox-output-errors/239184/1 "2007-09-19T12:38:56Z")

</div>

Hi,

I have this part of code  
[AS]  
var \_cb = \_this.getChildByName(“group\_cb”);  
trace(“\>\> “+\_cb)  
var getGroupNum:int = \_theBigArray.length/2;  
var i:uint;  
for (i=0;i\<getGroupNum;i++) {  
\_cb.addItem({label: \_theBigArray[i\*2][1], data: i_2});  
trace("addItem [label: “+\_theBigArray[i\*2][1]+” data "+(i_2)+”]”);  
}  
[/AS]

the output from trace is:

> \>\> [object ComboBox]  
> addItem [label: Antique Photo Border data 0]  
> addItem [label: Red Photo Border data 2]  
> addItem [label: Blue Photo Border data 4]  
> But when I clicked to scroll combobox it appear this error:

> TypeError: Error #1009: Cannot access a property or method of a null object reference.  
> at fl.containers::BaseScrollPane/fl.containers:BaseScrollPane::drawBackground()  
> at fl.controls::List/fl.controls:List::draw()  
> at fl.core::UIComponent/drawNow()  
> at fl.controls::List/scrollToIndex()  
> at fl.controls::SelectableList/scrollToSelected()  
> at fl.controls::ComboBox/open()  
> at fl.controls::ComboBox/fl.controls:ComboBox::onToggleListVisibility()  
> ArgumentError: Error #2025: The supplied DisplayObject must be a child of the caller.  
> at flash.display::DisplayObjectContainer/removeChild()  
> at fl.controls::ComboBox/close()  
> at fl.controls::ComboBox/fl.controls:ComboBox::focusOutHandler()

Why is getting this errors?